The present invention relates to a master carrier for magnetic transfer used for transfer of recorded information to a magnetic recording medium in a magnetic recording and reproducing apparatus of large capacity and high recording density, and in particular, to a master carrier for magnetic transfer and a method for transfer used for recording of servo signals, address signals, other normal video signals and audio signals, data signals, etc. to a magnetic recording medium of large capacity and high recording density.
With rapid progress and development of the use of digital images, the amount of information to be handled by personal computer or other devices is extensively increasing. With the increase of the amount of information or information content, there are strong demands on a magnetic recording medium, which has large capacity to record information, is available at lower cost and requires shorter time for recording and reading.
In a high density recording medium such as hard disk or in a large capacity removable type magnetic recording medium such as ZIP (Iomega Inc.), information recording area comprises narrower tracks compared with floppy disk. In order to scan the magnetic head accurately along the narrow tracks and to perform recording and reproduction of signals at high S/N ratio, it is necessary to carry out accurate scanning using tracking servo technique.
In a large capacity magnetic recording medium such as hard disk or removable type magnetic recording medium, there is provided a recording area where servo signals for tracking, address information signals, reproducing clock signals, etc. are recorded at a constant angular interval for each turn of the disk. The magnetic head scans over the track accurately while confirming and correcting the position of the head by reproducing these signals at a predetermined interval. These signals are recorded on the magnetic recording medium in advance during the manufacturing process of the magnetic recording medium, and this is called xe2x80x9cpreformatxe2x80x9d.
Because positioning accuracy is required for the recording of servo signals for tracking, address information signals, reproducing clock signals, etc., the preformat recording is carried out by the magnetic head with its position strictly controlled by a special-purpose servo recording system after the magnetic recording medium has been incorporated into the drive.
However, in the preformat recording of the servo signals, address information signals, reproducing clock signals, etc. by the magnetic head, recording is performed while the position of the magnetic head is strictly controlled by the special-purpose servo recording system, and this means that much time is required for the preformat recording. Also, with the increase of magnetic recording density, amount of signals to be recorded by the preformat recording increases, and this requires much more time.
Further, there are disadvantages in that transition of magnetization at the end of the track recorded by the preformat recording lacks steepness or sharpness because of the spacing between the head and the magnetic recording medium and because of spreading of the recording magnetic field caused by the shape of the recording head.
Also, when information is transferred from the master carrier for magnetic transfer, the external field having coercive force more than 3 times as high as that of the recording medium must be used so that the magnetization on the master carrier for magnetic transfer may not be demagnetized when excitation is performed by applying external magnetic field.
When a magnetic material in planar shape is partially magnetized, coercive force of the master carrier will be more than 6000 Oe because coercive force of the magnetic material used in the recording medium for high density recording is about 2000 Oe, and it is practically impossible to perform accurate magnetization by the magnetic head.
To solve these problems, the following method has been proposed in JP-A-10-010544: This is a method, which comprises the steps of forming irregularities, i.e. projections and recesses, to match information signals on the surface of a base material, bringing at least surface of a master carrier for magnetic transfer having ferromagnetic thin film formed on surface of the projections of the surface irregularities into contact with surfaces of sheet-like or disk-like magnetic recording medium having ferromagnetic thin film or ferromagnetic powder coating layer formed on it, or applying DC magnetic field to excite ferromagnetic material on the surface of the projections, and recording magnetization pattern corresponding to surface irregularities, or projections and recesses.
This is a method to form a predetermined format on the slave medium by bringing surface of the projections of the master carrier into contact with the magnetic recording medium to be preformatted, i.e. the slave medium, and by exciting the ferromagnetic material of the projections. It is possible to statically perform the recording without changing relative positions of the master carrier and the slave medium, and accurate preformat recording can be accomplished. Moreover, the time required for the recording is very short. That is, in the method for recording from the magnetic head as already described, the time required is usually several minutes to several tens of minutes, and the time required for the recording must be extended more in proportion to the recording capacity. However, in the magnetic transfer method, transfer operation can be completed within less than one second regardless of recording capacity or recording density.
In this recording method, when number of sheets to be recorded is not many, recording with high accuracy can be achieved. But, when the preformat is performed for a number of slave media, disturbance may occur on angular portions of the information recording area of the master carrier for magnetic transfer, or recording on the slave medium may be damaged, and it is difficult to perform recording on a number of sheets.
The present invention provides a master carrier for magnetic transfer to transfer recording information to a magnetic recording medium, said master carrier comprises a plurality of transfer information recording sectors made of ferromagnetic substance corresponding to the recording information to be transferred, non-magnetic material sectors to define the transfer information recording sectors are present between adjacent transfer information recording sectors, and surfaces of the transfer information recording sectors and surfaces of the non-magnetic material sectors are substantially positioned on and forming the same plane.
Also, the present invention provides the master carrier for magnetic transfer as described above, wherein thickness of each of the transfer information recording sectors is 20 to 1000 nm.
Further, the present invention provides the master carrier for magnetic transfer as described above, wherein said transfer information recording sector has coercive force (Hc) of not higher than 2500 Oe.
The present invention also provides the master carrier for magnetic transfer as described above, wherein said transfer information recording sector has saturation magnetic flux density (Bs) of not less than 0.3 T.
The present invention further provides the master carrier for magnetic transfer as described above, wherein said master carrier comprises a plurality of transfer information recording sectors made of ferromagnetic substance corresponding to the recording information to be transferred and being in form of projections on a substrate, and non-magnetic conductive layers formed between the transfer information recording sectors and the substrate.
Further, the present invention provides the master carrier for magnetic transfer as described above, wherein the conductive layer comprises non-magnetic metal.
Also, the present invention provides the master carrier for magnetic transfer as described above, wherein a protective film is formed on the surface of the transfer information recording sectors.
The present invention also provides the master carrier for magnetic transfer as described above, wherein said master carrier comprises a plurality of transfer information recording sectors made of ferromagnetic substance corresponding to the recording information to be transferred and being formed on a substrate, a space or a non-magnetic sector is present between each of the adjacent transfer information recording sectors, surface hardness of each of the transfer information recording sectors is not lower than 20 GPa, and a diamond-like carbon protective film of 3 to 30 nm in thickness is provided on the surface.
Further, the present invention provides the master carrier for magnetic transfer as described above, wherein the ferromagnetic substance is present only on the transfer information recording sectors, and not on the other portions.
Also, the present invention provides a method for magnetic transfer to transfer recording information to a magnetic recording medium, said method comprising the steps of providing a master carrier for magnetic transfer and a slave medium, and for bringing said master carrier and said slave medium into contact with each other, whereby said master carrier for magnetic transfer comprises a plurality of transfer information recording sectors with recording information for transfer magnetized thereon and being formed on a substrate, a space or a non-magnetic sector being provided on each of adjacent transfer information recording sectors, surface hardness of each of said transfer information recording sectors is not lower than 20 GPa, and a diamond-like carbon protective film of 3 to 30 nm in thickness is provided on the surface of the master carrier, and said slave medium has surface hardness of not lower than 1 GPa and has flexibility.
The present invention also provides a master carrier for magnetic transfer, which comprises a magnetic layer on a portion corresponding to information signal on the substrate surface, and a method for magnetic transfer by bringing the slave medium to receive transfer into contact with the master carrier and by applying magnetic field for transfer, wherein relationship between coercive force Hcs of the slave magnetic recording medium and the magnetic field for transfer is:
The present invention also provides the method for magnetic transfer as described above, wherein coercive 10 force Hc of the master carrier for magnetic transfer is not more than 600 Oe, and coercive force of the slave medium to receive magnetic transfer is not less than 1500 Oe.